A police patrol car in Palo Alto is creating controversy: it's now equipped with technology that can automatically read your license plate.

The device allows officers to automatically read license plates, scanning for stolen vehicles and cars with warrants connected to them.

The scanner immediately alerts police if they are looking at a stolen or lost vehicle. It can also be setup to alert police if the car is registered to someone with an arrest warrant outstanding.

Police say it's a powerful tool to fight crime, but civil rights advocates are expressing concerns about how the data is ultimately used.

"This is a very valuable tool," Palo Alto Police Sergeant Brian Philip said. "If you look at the case of a child abduction...We want to go and make sure we get the child back. This is a piece of technology that could aid us in doing something like that."

The readers store license information from all vehicles in the vicinity, not just suspect vehicles. According to the American Civil Liberties Union, that information can be shared with other law enforcement agencies.

The ACLU has said in the past it doesn't mind the readers scanning license plate numbers, it just doesn't like the fact that the agencies are storing data that tells authorities where an individual has traveled with his or her car and when.

The San Leandro Police Department also uses this technology. At least one East Bay driver requested all the info linked to his license plate be expunged. When police pulled up the information, 112 images of his car came up, along with his location.

"That's obviously something we're concerned about," Philip said. "That's why we're evaluating it now. But I think that the necessary steps are going to be taken when the policy's developed to ensure people's privacy is protected as much as we can protect it."

Santa Clara County police chiefs are scheduled to meet next week to discuss how the information will be used and stored.